Scale on my Corylus avellana ‘Contorta’?

(Question)

I have a 17 year old Corylus avellana ‘Contorta’, sometimes called Harry Lauder’s walking stick. It has always been very healthy, earlier this fall I noticed several dead branches, on closer inspection I can see bumps on the branches. The bumps are about 1/4 inch long maybe a little smaller and 1/8 inch high. This has been the year of the scale insect in southern Ontario but I have never seen them this big and I’m unsure if they are scale insects. They are mostly on the newer wood. I have cut of all the dead branches. I don’t know where to go from here. I have checked many resources and have not found any mention of scale on this shrub. The older branches seem fine. The shrub is located directly behind a garden pond full of fish so if this is scale any soloutions need to be non-toxic to the fish.

(Answer)

Your corkscrew hazel does not have scale. Unfortunately it has eastern filbert blight which is caused by the fungus Anisogramma anomala. I have seen this blight on many, many corkscrew hazels. It seems to be more prevalent in the last few years (although this is just an anecdotal observation).

In spring, spores are released from mature cankers of infected hazelnut trees and shrubs. Spores are spread by rain and splashing water droplets driven by wind. Young and developing shoots are highly susceptible to new infection. Newly infected shrubs do not show any symptoms for 12-15 months. The second summer following infection, the fungus begins to produce dark-brown to black spore-producing structures called “stroma” within cankers on infected stems. The mature stroma begin releasing spores the following spring. The fungus continues to produce new stroma and releases spores as the canker expands each year. Elongated, sunken cankers, expanding lengthwise on branches will be seen. Cankers are infected areas of sunken, dying tissues formed along a branch. Cankers expand from year to year and girdle the branch, resulting in branch dieback and eventually the shrub will die.

You may be able to prolong the life of your shrub by pruning out any diseased branches with cankers about 2-3 feet below the site of infection. Do not compost the diseased wood. Copper spray is used by nut farmers to control Eastern filbert blight, but it is not one of the allowable cosmetic pesticides for use on ornamental plants.